BACKGROUND AND PURPOSE: A crossover, double-blinded randomized controlled trial to investigate once-daily incremental vestibulo-ocular reflex (VOR) adaptation (IVA) training over 2 years in people with stable and chronic peripheral vestibular hypofunction. METHODS: Twenty-one patients with peripheral vestibular hypofunction were randomly assigned to intervention-then-control (n = 12) or control-then-intervention (n = 9) groups. The task consisted of either x1 (control) or IVA training, once daily every day for 15 minutes over 6-months, followed by a 6-month washout, then repeated for arm 2 of the crossover. Primary outcome: vestibulo-ocular reflex gain. Secondary outcomes: compensatory saccades, dynamic visual acuity, static balance, gait, and subjective symptoms. Multiple imputation was used for missing data. Between-group differences were analyzed using a linear mixed model with repeated measures. RESULTS: On average patients trained once daily 4 days per week. IVA training resulted in significantly larger VOR gain increase (active 20.6% +/- 12.08%, p = 0.006; passive 30.6% +/- 25.45%, p = 0.016) compared with x1 training (active -2.4% +/- 12.88%, p = 0.99; passive -0.6% +/- 15.31%, p = 0.68) (p < 0.001). The increased IVA gain did not significantly reduce with approximately 27% persisting over the washout period. x1 training resulted in greater reduction of compensatory saccade latency (p = 0.04) and increase in amplitude (p = 0.02) compared with IVA training. There was no difference between groups in gait and balance measures; however, only the IVA group had improved total Dizziness Handicap Inventory (p = 0.006). DISCUSSION AND CONCLUSIONS: Our results suggest IVA improves VOR gain and reduces perception of disability more than conventional x1 training. We suggest at least 4 weeks of once-daily 4 days-per-week IVA training should be part of a comprehensive vestibular rehabilitation program.

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